Orthodontic biassing device

ABSTRACT

An orthodontic biassing device comprising two spaced orthodontic elements is provided with an aperture in each element. The aperture may be in the form of a sleeve for receiving the body housings of an expansion screw. The sleeves are so configurated so as to interchangeably receive body housings having different lengths so that initial spacings between the two elements may be increased by replacing a shorter expansion screw which has been nearly totally extended from its respective body housings by an expansion screw with longer body housings. According to another embodiment, the spaced elements are in the form of resilient receptacles having elongated extensions connectable to teeth and openings which are configurated to receive the body housings by at least partially deforming the receptacles during insertion. Biassing devices which can be utilized both as expansion or contraction devices are described.

United States Patent [191 Wallshein 5] Sept. 3, 1974 ORTHODONTICBIASSING DEVICE [57] ABSTRACT [76] Inventor: Melvi w ll h i 8645 B Pk Anorthodontic biassing device comprising two spaced Brooklyn, NY. 11230Orthodontic elements is provided with an aperture in 4 each element. Theaperture may be in the form of a [22] Filed 1972 sleeve for receivingthe body housings of an expansion [21] Appl, N 310,575 screw. Thesleeves are so configurated so as to interchangeably receive bodyhousings having different lengths so that initial spacings between thetwo ele- [fi] :LS. Cll 32/14 E mems may be increased by replacing aShorter expam [58] FI-ltidC A616 7/00 i Screw hi has been nearly totallyextended le 0 earc 32/14 from its respective body housings by anexpansion screw with longer body housings. According. to an- [56]References Cned other embodiment, the spaced elements are in the UNITEDSTATES PATENTS form of resilient receptacles having elongated exten-618,105 1/1899 Knapp 32/14A ion nnec ble to teeth and openings which are3,529,353 9/1970 Schiaroli 32/14 A configurated to receive the bodyhousings by at least FOREIGN PATENTS OR APPLICATIONS partially deformingthe receptacles during insertion. 668 227 1/1950 6 t B 32/14 E Biassingdevices which can be utilized both as expan- 128350 7/1901 2:2 am sionor contraction devices are described. 915,317 7/1946 France 32/14 E 22Claims, 13 Drawing Figures Primary Examiner-Robert Peshock Attorney,Agent, or FirmFriedman & Goodman ORTHODONTIC BIASSING DEVICE BACKGROUNDOF THE INVENTION The present invention generally relates to orthodonticdevices, and more particularly to an orthodontic biassing device whichincludes an aperture in each one of two spaced elements, each aperturebeing configurated to interchangeably receive the body housings of meansfor separating or drawing together the two spaced elements.

Biassing devices in the form of palatal removable appliances are alreadywell known. One such device, the expansion device, serves as a retainingdevice which normally engages the teeth in some manner to stabilize theappliance in the mouth and serves as a support for various orthodonticappliances. A common form of expansion device is the expandable acrylicappliance having a spindle which is threaded at both ends but inopposite senses each end being meshingl-y engaged with another elementof the appliance. Rotation of the spindle causes the two elements eitherto come closer together or separate further apart. The disadvantage ofthe known expansion devices arises as a result of the manner in whichthe expansion screws are associated with the elements of the appliance.Thus, the prior art expansion screws are normally provided with bodyhousings at each end which are rigidly or permanently embedded in theacrylic. As frequently happens, the two elements, at least initiallyduring the tooth movement process, are spaced relatively close to oneanother the distance increasing as the teeth are separated in responseto forces supplied by the appliance on the teeth. When the acrylicelements are spaced from each other a distance substantiallycorresponding to the length of the threaded spindle, the particularexpansion device cannot serve much further purpose since furtherexpansion or separation of the acrylic elements results in thedisengagement of the threaded spindle form the body housings. With theknown appliances, new acrylic elements are required when furtherseparation is desirable since the body housings are permanently embeddedin the acrylic. This involved great time and expense. The same problemexists in connection with fixed palatal suture splitting applianceswhich include metal extensions soldered to clasps which are morepermanently connected to the teeth. The threaded body housings whichmesh with the spindle in this type of appliance define the elements ofthe appliance and are normally soldered directly or made integral withthe metallic extensions. As before, when the spindle has been fullyextended from the body housings, it is normally required to disconnectthe entire splitting appliance from the teeth and replace it with a newappliance provided with longer meshed body housings.

The disadvantages inherent in all of the prior art expansion devices hasbeen the difficulty and expense with which these applianceswere'interchanged once an existing appliance became too short for theintended application.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide an orthodontic biassing device which is notpossessed of the disadvantages known in similar devices.

It is another object of the present invention to provide a biassingdevice which is simple in construction and economical to manufacture.

It is an additional object of the invention to provide a biassing devicewhich has two elements each of which includes connecting means for beingconnected to biassing means for separating or drawing the elementstogether.

It is another object of the present invention to provide a biassingdevice of the type under discussion which includes a screw and two endbody housings each of which is meshed with the same screw at anotherend, the body housings being readily removable and interchangeable.

It is yet another object of the present invention to provide a biassingdevice having two orthodontic elements, each having an aperture forinterchangeably receiving the meshed body housings of a biassing screw.

It is a further object of the present invention to provide a biassingdevice as described above which interchangeably accepts biassing screwshaving various body housing lengths to thereby provide different initialspacings between the orhtodontic elements forming the biassing device.

It is still a further object of the present invention to provide abiassing device in the form of a fixed palatal suture splittingappliance having two spaced elements which includes interchangeable bodyhousings of biassing screws which are readily insertable and removablefrom the spaced appliance elements.

It is yet a further object of the present invention to provide anorthodontic biassing device having two spaced elements which includesinterchangeable biassing means provided between the two spaced applianceelements said biassing means being so arranged so as to apply a biassingforce to the two spaced elements.

Although the description that follows mostly concerns expansion devices,it should be clear that the invention similarly contemplates contractionbiassing devices. Thus, an expansion screw can act as a contractiondevice if it is turned in a reverse direction. Also, where a compressionspring is described, it should be clear that a spring under tension maybe substituted to produce an opposite effect.

In order to achieve the above objects, as well as others which willbecome apparent hereafter, an orthodintic biassing device in accordancewith the present invention comprises support means in the form of twospaced orthodontic elements at least one of which is provided withconnecting means. Adjustable biassing means are provided which extendbetween said two elements, said biassing means having at least a portionwhich engages and interchangeably connects to said connecting means. Inthis manner, the space between curely positioned in each aperture. Saidbiassing means includes two threaded body housings and a threadedspindle meshingly engaged in said housings in such a manner thatrotation of said spindle changes the spacing between said housings andthereby also between said elements. Each of said housings is removablymounted in a respective sleeve means. With respect to all of theembodiments, said apertures are adapted to interchangeably receivethreaded body housings having different overall lengths so as to providedifferent initial spacings between the appliance elements.

According to one presently preferred embodiment, the exterior dimensionsof said biassing means housings are so selected so that the latter arereceived in said apertures in pressure fitting relation.

With respect to all of the biassing devices in accordance with thepresent invention, the biassing screws, including the end body housingswhich support the spindle at both ends thereof are interchangeablyinsertable in pressure fitting relation internally of the apertures ineach of the respective spaced elements.

According to another preferred embodiment, the biassing device is in theform of a biassing cylinder which comprises two concentric cylinders onehaving a slightly smaller diameter than the other so that the formerslidingly fits inside the latter. A stressed spring provided inside thetwo cylinders tends to force the two cylinders in opposite directionsalong the axis of the cylinders. Each of the cylinders has a diameterselected to fit into one of the apertures of the biassing device. Whenthe coil is mounted in the cylinders in a compressed state, thecylinders exert separating biassing forces on the two elements whichcontain the same. However, the coil may also be mounted in the cylindersunder tension in which case the cylinders draw the two elements towardseach other.

The facility with which the biassing means are interchanged in all ofthe biassing devices in accordance with the present inventiongreatly-reduces the time which has been expanded in the past in changingbiassing devices. In addition to the increased convenience, an importantfeature of the present invention is that the same biassing deviceelements may be re-used the only items which must be interchanged arethe acutal biassing means which are engaged with the elements. Also, theoriginal shorter biassing means may similarly be re-used and thisfurther decreases the cost of such biassing devices, when the latter areintended to move the elements a great distance relative to each otherduring the lifetime of the appliance or device.

BRIEF DESCRIPTION OF THE DRAWINGS With the above and additional objectsand advantages in view, as will hereinafter appear, this inventioncomprises the devices, combinations and arrangements of partshereinafter described and illustrated in the accompanying drawings of apreferred embodiment in which:

FIG. 1 is a fragmented top plan view in schematic of an expansion orcontraction device in accordance with the present invention;

FIG. 2 is a side elevational view, partly in crosssection, showing theexpansion or contraction device of FIG. 1;

FIG. 3 is a side elevational view, partly in crosssection, showing theexpansion or contraction device of FIG. 1;

FIG. 4 is an exploded view in perspective showing schematically therelationship between the expansion screw and the sleeves which receivethe same;

FIG. 5 is a perspective view of an expansion screw similar to that shownin FIG. 4, but having longer body housings configurated to be insertedinto the sleeves of FIG. 4;

FIG. 6 is a fragmented side view, partly in crosssection, of onepossible connecting means configurated for connecting an element of abiassing device to a portion of a biassing means;

FIG. 7 is a perspective view of a fixed palatal suture splittingappliance having expansion screw elements or receptacles whichinterchangeably receive expansion screw housings having various overalllengths, and fur ther showing an expansion screw just prior toengagement with the appliance;

FIG. 8 is another embodiment of a fixed palatal suture splittingappliance having lateral flanges from which the metallic extensionsextend;

FIG. 9 is a cross-section of the appliance-shown in FIG. 8, taken alongline XX;

FIG. 10 is an enlarged perspective of one end of a receptacle elementshown in FIG. 8, showing the details of a retaining tab;

FIG. 11 is a cross-section of an expansion or contraction device inaccordance with the present invention which has two concentriccontainers and which may be utilized with the above describedembodiments in place of an expansion screw;

FIG. 12 is a cross-section of compression means similar to that of FIG.1 1, wherein one container is replaced by a piston; and

FIG. 13 is similar to FIG. 12, but for tension means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS of a plastic removableappliance l0, commonly in the form of an acrylic appliance, comprisestwo acrylic elements or members 12, 14 which are spaced from one anotheran adjustable distance, as to be described. In the description thatfollows, it should be clear that expansion devices may also be utilizedas contraction devices.

Connecting the two acrylic elements 12, 14 is an expansion screwgenerally designated by the reference numeral 22 whose construction perse is well known in the art. Referring also to FIG. 2, the expansionscrew 22 generally comprises a body housing 16 and a body housing 20each of which is provided with an internal thread which respectivelymeshes opposite screw portions 24, 26 of aspindle. Positioned betweenthe two ends 24, 26 of the spindle is a non-threaded spindle engagingportion 28 which is provided with radial holes 30 adapted to be engagedby a special tool or simply an elongated pin which may fit in the holes.The body housing 16 of the expansion screw 22 engages or is insertedinto a connecting means in the form of a sleeve 18 which is enclosed inthe acrylic element 12. Similarly, a sleeve 18 is embedded in theacrylic element 14. Advantageously, the exteriors of the sleeves 18 areprospacing between the acrylic elements 12, 14, while the expansionscrew is fully contracted, may be increased at will. Usually, a newexpansion screw having longer body housings is desirable when anexpansion screw, having shorter body housings, can no longer be expandeddue to the fact that the spindle ends of the expansion screws are almostfully extended from their respective body housings.

In the case of acrylic appliances, it is advantageous to provide atleast one guide pin 21, and preferably two guide pins 21 on each side ofthe expansion screw as shown in FIG. 1. The guide pins 21 prevent therelative rotation of the acrylic elements relative to each other aboutthe spindle of the expansion screw. Presently available expansion screwsare frequently provided with guide pins and therefore no additionalguide pins need be provided.

According to the presently preferred embodiments, wherein the inventionis utilized with a plastic, e.g., acrylic, removable appliances, isillustrated in FIGS. 3-5. In FIG. 3, the acrylic element is shown to beprovided with a sleeve 18 which is embedded in the acrylic. As mentionedabove, the sleeve 18 is typically provided with a roughened exteriorsurface so as to be better retained in the acrylic in order to withstandthe substantial forces exerted on the sleeve. The sleeve is ofcylindrical configuration. For the purposes of the present applicationas well as the claims, the term cylindrical shall not be construed tomerely include circular cylindrical shapes but includes any cylindricalshape,

e.g., such as an oval or square. More specifically, the shape of thesleeve 18 is selected to conform with the exterior shape of the bodyhousings which are to be contained therein. The sleeves and the bodyhousings form mating portions of a connecting means for connecting theexpansion screw to the elements.

According to one presently preferred embodiment of the sleeves 18, theinterior dimensions of the sleeves are selected to closely correspond tothe exterior dimensions of the body housings so that the housings matewith the sleeves with little clearance therebetween. Preferably, theinternal dimensions of the sleeves are so selected so that a press-fitis obtained when the body housings are urged into the sleeves. However,this is not a critical feature since the expansion screws 22 arenormally urged or biased in such a manner that the body housings areforced into the acrylic elements. Therefore, there is no danger,practically, of the body housings from coming out of the sleeves.

Accordingly to a modification, the sleeves are provided with radiallyinwardly projecting annular projections 34 while the body housings areprovided with annular grooves 32 configurated to receive the projectionsin the mated condition of the body housings in the sleeves. Thus, whenthe body housings are fully inserted into their corresponding sleeves,the annular projections snap into the annular grooves and the housing isretained in the sleeve. However, as above, there is no practical problemwith the body housings leaving the sleeves because of the normallyexpanded condition of the expansion screw.

In FIGS. 4 and 5, there is schematically illustrated the manner in whichthe present invention is utilized. The acrylic elements in which thesleeves 36, 38 are embedded are not shown in order to simplify thedrawing. However, it is to be understood that the sleeves 36, 38, areeach embedded in acrylic elements as shown in FIGS. l-3. The expansionscrew 22 includes body housings 42, 44 which have a predetermined lengthalong the axis defined by the expansion screw. As before, although thebody housings are shown to be in the form of right circular cylinders,this is only so shown for illustrative purposes and the cross-section ofthe body housings may be of any shape whatsoever. Typically, bodyhousings commonly available have oval crosssections.

When the screw portions 24, 26 of the spindle 22 are fully extended ornearly fully extended from the body housings 42, 44 and no furtherextension is possible, the expansion screw 22 is disengaged from theacrylic elements by urging the body housings 42, 44 from the sleeves 36,38.

The next sized expansion screw 22', having longer body housings 42, 44'and shown in FIG. 5, is engaged with the sleeves 36, 38. Because thebody housings 42', 44' of the new expansion screw 22' are longer alongthe general axis defined by the expansion screw, the initial spacing ofthe sleeves 36, 38, and therefore also the acrylic elements, with thenew expansion screw 22 fully contracted may be selected to beapproximately equal to that with the original expansion screw 22 fullyextended. Now, should the spacing between the acrylic elements befurther increased, the new expansion screw 22' can be expanded byturning the spindle engaging portion 28 as before. It should be notedthat the acrylic elements need not be replaced. Also, the originalexpansion screw 22, which has been replaced by a longer expansion screw22, may, but need not, be discarded as with prior art designs.

The above-described connecting means have been describedas sleevesforming apertures in the elements l2, 14. However, it should be clearthat the sleeves 18 may be omitted as shown in FIG. 6. Here, theconnecting means comprises an aperture 19 formed directly in the acrylicmember 12. The internal dimensions of the aperture 19 can be selected toreceive a body housing or a portion of a pin 21 of a biassing means 22.The aperture 19 and the pin 21 can each be threaded so as to meshinglyengage each other. When not so threaded, the element 12 may be providedwith an annular groove 34a while the pin is provided with acorrespondingly dimensioned annular projection 32a which can snap intothe groove 34a.

The same principal described in connection with plastic or acrylicremovable appliances can also be utilized with respect to expansiondevices commonly termed fixed palatal suture splitting appliances. Suchappliances known in the prior art have generally consisted of anexpansion screw to which are welded or soldered metallic extensionswhich include tooth engaging means at the free ends thereof. As with theacrylic appliances of the prior art, the expansion screws in the priorart could not be easily changed so that when an original expansion screwwas fully expanded, it was a difficult and time consuming task to removethe metal extensions and re-solder them on a new expansion screw havinglonger body housings.

This problem is aleviated, with respect to the palatal suture splittingappliances, by providing holders 50 as shown in FIG. 7. The holders 50are in the general shape of an oval cylinder each having an open and aclosed end 52 the open end being shown as a front opening 56 in FIG. 6.The holders 50 are also provided with side openings 58 which run alongthe axial length of the cylindrical holders. Connected to the closedends 52 are metal extensions 54 which are connected to tooth holdingmeans in a conventional manner. As described above, the oval nature ofthe holders 50 is merely illustrative and any other cross-sectionalconfiguration of the holders may be utilized.

The palatal suture splitting appliances differ in one important respectto the acrylic appliances in that the holders 50 are normally rigidlyheld in position by means of the metal extensions and fixed due to theconnections of the metal extensions to the teeth. Accordingly, guidepins described in connection with the acrylic appliances need not beutilized.

The holders 50 may be made from any suitable relatively rigid materialwhich, however, is sufficiently flexible so as to permit the insertionof the body housings 16, into the holders 50 through the side openings58. The height of the side openings 58 are selected to be somewhatsmaller than the height of the body housings l6, 18 so that the latterare retained in the holders 50 after they have been forced therein. Whenthe body housings 16, 20 are urged into the holders 50, therefore, theside openings 58 are at least partially deformed and enlarged so as topermit entry ofthe body housing 16, 20. To remove the expansion screw22, it is merely necessary to pull the latter in the direction of theside openings 58 so as to enlarge the side openings and so as to releasethe body housings 16, 20.

As with the acrylic appliance, when the holders or elements 50 are fullyspaced from each other as a result of a fully expanded condition of anexpansion screw 22 associated with the elements, that expansion screwmay be removed from the holders 50 as described above and a newexpansion screw having longer body housings 16, 20 may be placedtherein.

FIGS. 8-10 illustrate another embodiment of the palatal suture splittingappliance of FIG. 7 wherein the elements 60 are slightly modified tohave cylindrical holders 64 which may be of the same cross-sectionalconfiguration as the holders 50. However, the holders 64 are providedwith an elongated slot 66 along the lower end of the holders 64 asviewed in FIGS. 8-10. Extending from the holders 64in the region of theopenings 66 are tabs 62 which serve as supports to which the metalextensions 54 may be soldered. The holders 60 have a front open end andan opposite end which is provided with a screw abutting portion 68 asbest seen in FIG. 10. The portions 68 serve to retain the body housings16, 20 of the expansion screws 22 in the holders 64 when the expansionscrews are expanded.

The embodiment shown in FIG. 7 permits the replacement of expansionscrews through a side of the holders 50. On the other hand, the holders60 shown in FIGS. 8-10 permit the replacement of expansion screwsthrough the lower or bottom slots 66 of the holders which generally runalong the axis of the expansion screw. In some instances, it is easierto interchange an expansion screw with the embodiment as shown in FIGS.8-10, particularly when there is little room to maneuver inside themouth.

An expansion biassing means is illustrated in FIG. 1 l and generallydesignated by the reference numeral 70. The biassing means generallycomprises an inner container 72 and an outer container 74. Thecross-sections of the containers 72, 74 are preferably non-circular sothat the elements connected to respective containers do not turnrelative to one another about an axis generally defined by the elongatedcontainers. The outer dimensions of the inner container 72 issubstantially equal to the inner dimensions of the outer container 74.In this manner, the inner container is slidably mounted in the outercontainer. Each of thecontainers has an open end on the side of theother container while having a closed end on the side facing away fromthe other container. Resilient means in the form of a helical spring 76is provided which extends between the closed ends of the two containers.When the helical spring is not compressed, the two containers are spacedrelative to each other in a predetermined condition. However, when thetwo containers are moved in such a manner as to futher insert container72 into the outer container 74 and thereby compress the helical spring76, the latter generates forces which tend to restore the two containersto their normal or predetermined condition. The external dimensions ofthe two containers are so selected so that they may be inserted intoapertures or sleeves, as with the acrylic appliances, or into holders,such as with the palatal suture splitting appliances.

It is clear that the axial lengths of both the inner and outercontainers 72, 74 respectively can be selected to be any convenientvalues as short or as long as desired.

In using the biassing expansion device 70, the latter is firstcompressed or shortened so that the inner container 72 is forcedsomewhat into the outer container 74. The extent of compression may varyand is so selected so that the overall length of the device isapproximately equal to the initial spacing of thetwo elements of theexpansion device or appliance. The opposite ends of the biassing device70 are then respectively positioned either inside the expansion sleevesor in the holders, as described above. Once positioned in the sleeves orholders, the biassing device 70, being in a compressed state, supplies aconstant separating and biassing force on the two elements of theexpansion appliance. This constitutes an advantage over conventionalexpansion devices which must periodically be expanded by turning athreaded spindle.

According to another advantageous feature of the biassing device 70,these may be provided in various length containers similarly to thevarious length body housings in connection with expansion screws. Also,the biassing device 70 may be provided with variable constant springs sothat greater or lesser biassing forces are applied to the respectiveremovable appliance elements. Both the length as well as the springconstants may be standardized for a convenient selection. In all otherrespects, the expansion device 70 may be utilized as described above inconnection with expansion screws, i.e., the biassing device may beinterchanged once the latter has reached a condition wherein thebiassing spring is no longer compresses and therefore no longer has anytendency to increase the spacing of the expansion device elements.

Different embodiments of the biassing device 70 of FIG. 11 are shown inFIGS. 12 and 13. In FIG. 12 biassing means 80 includes a container 82which has an opening 83 at one end thereof. Both the container 82 aswell as the opening 83 have non-circular crosssections to preventrotation of the elements connected thereto as described above. A pistoncooperates with the container and includes a shaft or pin 84 having across-section which corresponds to the cross section of the opening 83and which is slidingly mounted in the latter. An abutting member 86 isconnected to the pin 84 and is slidingly mounted inside the container82. When the pin 84 is moved so as to compress a spring 88, the latterbiasses the piston and container in opposite directions so as to extendthe piston and revert the spring to its unstressed state. The pin 84can, for example, be mounted in an aperture such as shown in FIG. 6. InFIG. 13, the biassing means 90 is almost identical to that shown in FIG.12 except that a spring 98 now abuts against the openend of thecontainer 92 and the abutting member 96 while being concentricallymounted with the pin 94. Here, when the pin is moved so as to compressthe spring 98, the latter biasses the piston and container so as tocontract the biassing means 90. Otherwise, the operation of the biassingmeans 80, 90 is similar to that of biassing means 70. The pin 94 is alsoshown to have a free end portion having enlarged external dimensionswhich may, in some cases, be more suitable for mating with an aperturein an element as described above.

Although the connecting means has been described in terms of an aperturein an element, eg elements l2, 14, it is possible to reverse the orderand provide an aperture in the biassing means and a projection on theelement which mates with aperture. It is also contemplated that otherforms of connecting means, other than apertures and mating parts, whichcan easily engage and disengage can also be used the novel featureresiding in the interchangeability of biassing means with respect toelements of biassing devices.

By connecting the ends of the helical spring 76 under tension to theclosed ends of the containers 72, 74, the biassing device 70 may also beused as a contraction device. Generally, as described above, anyexpansion device may be utilized as a contraction device and vice versa.

Advantageously, all the above-described biassing devices includeconventional means (not shown) for preventing the total separation ofthe two elements. In the case of the biassing devices utilizing theexpansion screws 22, the meshed relationship between the spindles andthe body housings together with the press-fits between the housings andthe cylindrical receptacles are usually sufficient to preventseparation. In the case of biassing devices 70, conventional means (notshown) may be utilized to prevent separation of containers 72, 74 andthereby also separation of the elements due to the press-tittherebetween.

Numerous alterations of the structure herein disclosed will suggestthemselves to those skilled in the art. However, it is to be understoodthat the present disclosure relates to a preferred embodiment of theinvention which is for purposes of illustration only andis not to beconstrued as a limitation of the invention.

What is claimed is:

l. Orthodontic biassing device comprising two spaced orthodonticexpansion or contraction elements each suitable for engaging one or moreteeth; an elongate biassing assembly extending between said elements,said biassing assembly having an adjustably variable length; andconnecting means for frictionally connecting each end portion of saidbiassing assembly to a respective element, said connecting meansincluding mating portions, said mating portions being conectable anddetachable from each other by relative movement between the latter andthe former in a single plane with sufficient force to overcome thefrictional forces developed by said connecting means, whereby biassingassemblies having different overall lengths can be interchanged.

2. The biassing device as defined in claim 1, wherein said two elementscomprise a plastic appliance, and wherein said mating portions comprisea sleeve embedded in each element of said appliance dimensioned toreceive another end portion of said biassing assembly.

3. Orthodontic biassing device as defined in claim 1, wherein saidconnecting means comprises snap fastener means.

4. The biassing device as defined in claim 1, wherein said two elementscomprise a removable plastic appliance.

5. The biassing device as defined in claim 1, wherein said two elementscomprise an acrylic appliance.

6. The biassing device as defined in claim 1, wherein said two elementscomprise elongated members including means at the respective free endsthereof for engaging a tooth.

7. The biassing device as defined in claim 1, wherein said two elementscomprise a palatal suture splitting appliance.

8. The biassing device as defined in claim 1, wherein said connectingmeans comprises an aperture in each element, and sleeve means securelypositioned in each aperture, said biassing assembly including twothreaded body housings and a threaded spindle meshingly engaged in saidhousings in such a manner that rotation of said spindle changes thespacing between said housings and thereby also between said elements,each of said housings being removably mounted in a respective sleevemeans.

9. The biassing device as defined in claim 2, wherein each sleeve isprovided with a roughened exterior surface to thereby provide animproved gripping surface when embedded in the plastic appliance.

10. The biassing device as defined in claim 8, wherein said aperturesare configurated to interchangeably receive threaded body housingshaving different overall lengths.

11. The biassing device as defined in claim 1, wherein each elementcomprises a substantially cylindrical and at least partially resilientcontainer having one open and one closed end, and having a lateralopening along the length of said container, and elongated extensionsconnected to said container in the region of said closed end whichincludes means for connection to a tooth, said open end and said lateralopening having dimensions to permit the reception of a mating portion ofsaid biassing assembly therein by at least partially deforming saidcontainer and thereby permit the removable insertion of said matingportion interiorly of said container.

12. The biassing device as defined in claim 1, wherein each elementcomprises a substantially cylindrical and 13. The biassing device asdefined in claim 1, further comprising guide means extending betweensaid elements and spaced from said biassing assembly for preventingrelative rotation of said elements about said biassing means.

14. The biassing device as defined in claim 1, wherein said biassingassembly comprises a first container having an open end, a secondcontainer having an open end and so dimensioned that said firstcontainer receives said second container through the open end of thesaid first container, the open end of said second container beingpositioned interiorly of said first container, and resilient meansacting on said first and second containers for generating a force whichtends to change the relative spacing between said containers when saidsecond container is moved relative to said first container beyond anormal relative position of said containers against the action of saidresilient means.

15. The biassing device as defined in claim 14, wherein said resilientmeans comprises a helical spring extending between said two containers.

16. The biassing device as defined in claim 1, wherein said biassingassembly comprises a container having an opening at one end, pistonmeans at least a portion of which partially extends through said openend, and resilient means for urging said piston means to move relativeto said container when said resilient means is placed under stress.

17. The biassing device as defined in claim 1, wherein said matingportions comprise an aperture in each element configurated'to receive anassociated end portion of said biassing assembly.

18. The biassing device as defined in claim 17, wherein the exteriors ofsaid biassing assembly end portions are dimensioned to be receivable insaid apertures in pressure fitting relation.

19. The biassing device as defined in claim 17, wherein the exteriors ofsaid biassing assembly end portions are dimensioned to be receivable insaid apertures in snap fitting relation.

20. The biassing device as defined in claim 16, wherein said resilientmeans comprises a helical spring under compression and acting on saidpiston to decrease the length of said biassing assembly.

21. The biassing device as defined in claim 16, wherein said resilientmeans comprises a helical spring under compression and acting on saidpiston to increase the length of said biassing assembly.

22. Orthodontic biassing device comprising two spaced orthodonticelements each suitable for engaging one or more teeth and each providedwith an opening, said elements being arranged to position said openingsin spaced relation in opposition to each other; and an elongateadjustable biassing assembly extending between said elements, saidbiassing assembly having an adjustably variable length and havingopposing end portions detachably and interchangeably receivable inrespective openings of said elements, insertion and removal of said endportions being effected by longitudinal movement of said biassingassembly relative to an associated opening, whereby biassing action isprovided by the biassing device by changing the length of said biassingassembly and whereby the latter may be connected and disconnected fromone or both elements by being longitudinally inserted or removed fromone or both of said openings of associated elements.

1. Orthodontic biassing device comprising two spaced orthodonticexpansion or contraction elements each suitable for engaging one or moreteeth; an elongate biassing assembly extending between said elements,sAid biassing assembly having an adjustably variable length; andconnecting means for frictionally connecting each end portion of saidbiassing assembly to a respective element, said connecting meansincluding mating portions, said mating portions being conectable anddetachable from each other by relative movement between the latter andthe former in a single plane with sufficient force to overcome thefrictional forces developed by said connecting means, whereby biassingassemblies having different overall lengths can be interchanged.
 2. Thebiassing device as defined in claim 1, wherein said two elementscomprise a plastic appliance, and wherein said mating portions comprisea sleeve embedded in each element of said appliance dimensioned toreceive another end portion of said biassing assembly.
 3. Orthodonticbiassing device as defined in claim 1, wherein said connecting meanscomprises snap fastener means.
 4. The biassing device as defined inclaim 1, wherein said two elements comprise a removable plasticappliance.
 5. The biassing device as defined in claim 1, wherein saidtwo elements comprise an acrylic appliance.
 6. The biassing device asdefined in claim 1, wherein said two elements comprise elongated membersincluding means at the respective free ends thereof for engaging atooth.
 7. The biassing device as defined in claim 1, wherein said twoelements comprise a palatal suture splitting appliance.
 8. The biassingdevice as defined in claim 1, wherein said connecting means comprises anaperture in each element, and sleeve means securely positioned in eachaperture, said biassing assembly including two threaded body housingsand a threaded spindle meshingly engaged in said housings in such amanner that rotation of said spindle changes the spacing between saidhousings and thereby also between said elements, each of said housingsbeing removably mounted in a respective sleeve means.
 9. The biassingdevice as defined in claim 2, wherein each sleeve is provided with aroughened exterior surface to thereby provide an improved grippingsurface when embedded in the plastic appliance.
 10. The biassing deviceas defined in claim 8, wherein said apertures are configurated tointerchangeably receive threaded body housings having different overalllengths.
 11. The biassing device as defined in claim 1, wherein eachelement comprises a substantially cylindrical and at least partiallyresilient container having one open and one closed end, and having alateral opening along the length of said container, and elongatedextensions connected to said container in the region of said closed endwhich includes means for connection to a tooth, said open end and saidlateral opening having dimensions to permit the reception of a matingportion of said biassing assembly therein by at least partiallydeforming said container and thereby permit the removable insertion ofsaid mating portion interiorly of said container.
 12. The biassingdevice as defined in claim 1, wherein each element comprises asubstantially cylindrical and at least partially resilient containerhaving an open and a closed end, and having a lower opening along thelength of said container bounded by two outwardly extending flanges; andhaving elongate extensions connected to said flanges which include meansfor connection to a tooth, said open end and said lower opening havingdimensions to permit the reception of a mating portion of said biassingassembly therein by at least partially deforming said container andthereby permit the removable insertion of said mating portion interiorlyof said container.
 13. The biassing device as defined in claim 1,further comprising guide means extending between said elements andspaced from said biassing assembly for preventing relative rotation ofsaid elements about said biassing means.
 14. The biassing device asdefined in claim 1, wherein said biassing assembly comprises a firstcontainer having an open end, a second container hAving an open end andso dimensioned that said first container receives said second containerthrough the open end of the said first container, the open end of saidsecond container being positioned interiorly of said first container,and resilient means acting on said first and second containers forgenerating a force which tends to change the relative spacing betweensaid containers when said second container is moved relative to saidfirst container beyond a normal relative position of said containersagainst the action of said resilient means.
 15. The biassing device asdefined in claim 14, wherein said resilient means comprises a helicalspring extending between said two containers.
 16. The biassing device asdefined in claim 1, wherein said biassing assembly comprises a containerhaving an opening at one end, piston means at least a portion of whichpartially extends through said open end, and resilient means for urgingsaid piston means to move relative to said container when said resilientmeans is placed under stress.
 17. The biassing device as defined inclaim 1, wherein said mating portions comprise an aperture in eachelement configurated to receive an associated end portion of saidbiassing assembly.
 18. The biassing device as defined in claim 17,wherein the exteriors of said biassing assembly end portions aredimensioned to be receivable in said apertures in pressure fittingrelation.
 19. The biassing device as defined in claim 17, wherein theexteriors of said biassing assembly end portions are dimensioned to bereceivable in said apertures in snap fitting relation.
 20. The biassingdevice as defined in claim 16, wherein said resilient means comprises ahelical spring under compression and acting on said piston to decreasethe length of said biassing assembly.
 21. The biassing device as definedin claim 16, wherein said resilient means comprises a helical springunder compression and acting on said piston to increase the length ofsaid biassing assembly.
 22. Orthodontic biassing device comprising twospaced orthodontic elements each suitable for engaging one or more teethand each provided with an opening, said elements being arranged toposition said openings in spaced relation in opposition to each other;and an elongate adjustable biassing assembly extending between saidelements, said biassing assembly having an adjustably variable lengthand having opposing end portions detachably and interchangeablyreceivable in respective openings of said elements, insertion andremoval of said end portions being effected by longitudinal movement ofsaid biassing assembly relative to an associated opening, wherebybiassing action is provided by the biassing device by changing thelength of said biassing assembly and whereby the latter may be connectedand disconnected from one or both elements by being longitudinallyinserted or removed from one or both of said openings of associatedelements.